Four Flies on Grey Velvet - Review (Blu-ray version)

Roberto Tobias (Michael Brandon) is a drummer in a rock band who has noticed a man following him for the last several days. Angered by this, he confronts the stranger in an abandoned theater to find out what he wants. The man claims he does not know what Roberto is talking about, and pulls a switchblade. The two struggle, and Roberto accidentally stabs the man, who falls into an orchestra pit, lifeless.

To make matters worse, someone in a bizarre puppet mask has been hiding in the upper wings of the theater and takes incriminating photographs of Roberto holding the bloody knife. Roberto flees, but the next day he receives the dead man's ID in the mail. It becomes apparent that the masked figure has no interest in going to the police, and instead wants to drive Roberto mad with fear and paranoia. But why?